Device for amplifying electrical currents.



No. 854,120. PATENTED MAY 21, 1907.

J. s. STONE. DEVICE FOR AMPLIFYING ELECTRICAL GURRENTS.

APPLICATION FILED MAY 23, 1906.

2 SHEETS-SHEET 1.

Fig.1.

\X/IT JE-EEE: 5= I Vs; TIDE PATENTED MAY 21, 1907.

J. S. STONE.

DEVICE FOR AMPLIPYING ELECTRICAL GURRENTS.

APPLIGATION FILED MAY 23, 1906.

2 SEEETS-SHEET 2.

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UNITED STATES PATENT OFFICE.

JOHN sTONE sToNE, OE CAMBRIDGE, MASSACHUSETTS, ASSIGNOR To JOHN A.CHRYSTIE, Louis DUNCAN, AND WALTER u. TURNER, ALL OE NEW YORK, N. Y.

DEVICE FOR AMPLIFYING ELECTRICAL CURRENTS.

Specification of Letters Patent. Application filed May 23, 1906. SerialNo. 318,306.

No. 854,120. .E'atented May 21, 1907.

To all whom it may con/earn.-

Be it known that 1, JOHN STONE STONE, a of my invention. citizen of theUnited States, and a resident of In the drawin s, Cambridge, in thecounty of Middlesex and I my invention, State of Massachusetts, haveinvented a new and useful Improvement in Devices for AmplifyingElectrical Currents, of which the fol lowing is a specification. I

My invention relates fying electrical currents, however produced, whichvary in accordance with the sonorous ments without departing from theprinciple Figure 1 is a plan view of s owing the circuit arrangements indiagram. Fig. 2 is a longitudinal section taken on the line 22 ofFig. 1. Fig.

Fig. 2.

in the drawings, D D represent rollers on which the magnetizable wire Cis wound. By mechanisms which arev now well known and which form no )artof my invention, the magnetizable wire has its magnetism modified inaccordance with the sonorous vibrations which accompany vocal or othersounds and is moved past the electromagnet A, being maintained. alwaysclosely adjacent to the core of said electromagnet. As is now wellunderstood by those skilled in the art of telegraphones, the relativemotion produced between said magnetizable member C and said to devicesfor amplivibrations accompanying vocal or other sounds, and it relatesmore particularly to devices of such character which are adapted toamplify without distortion the currents, and hence the sounds producedby telegra- The primary object of my invention is to produce a devicefor amplifying such electrical currents, in which the diaphragm orarmature which is actuated by said currents and which in turn serves toactuate the movable electrode of a microphonic transmitter is maintainedin a condition of stable equilibrium and a secondary object of myinvention is to provide for amplifying without the circuit of thesolenoid which constitutes part of said electromagnet and if a telephonereceiver be included in circuit with said so lenoid sound waves will beproduced corresponding more Or less accurately to the original sonorousvibrations whereby the magnetism of the member C originally was varied.These sound waves, however, will be exceedingly minute, and althoughvarious attempts have been made to amplify the currents produced bytelegraphones and the re sulting sounds produced by said currents intelephone receivers, I am advised that as yet no such attempt has beencommercially successful.

As shown in Fig. 1, the circuit of the solenoid which constitutes partof the electromagnet A, includes the serially-connected coils 6, 6 whichsurround cores secured to the permanent magnet 6, the cores of saidcoils and said permanent magnet being secured to the cross piece 5 ofbrass or other non-magnetic metal. In lieu of a telephone diaphragmoperated upon by the magnetic flux created by the currents flowing inthe coils 6 for reproducing as sonorous vibrations the electricvibrations developed in the circuit of the coils a device distortion thecurrents, and hence the sounds, produced by telegraphones.

With these objects in view my invention consists in a device foramplifying electrical currents, in which a diaphragm or armature and themovable electrode of a microphonic transmitter are maintained in acondition of stable equilibrium between a magnetic force and an opposingmechanical force whichvaries for all positions of said diaphragm andelectrode directly as said magnetic force, and such mechanical forcemay, with a sufiicient degree of approximation, be applied by an elasticmember the tension of which increases as the square of its deflection.

My invention may best be understood by having reference to the drawingswhich accompany and form a part of this specification, and whichillustrate one form of apparatus and arrangement of circuits whereby thehereinbefore mentioned objects may be carried into effect, although itis to be understood that I do not limit myself to the particular Vembodiments therein illustrated inasmuch 6 by the motion of themagnetizable member as many modifications may be made both in C past theelectromagnet A, 1 cause said flux the apparatus and in the circuitarrange- '1 to produce relative movements between the electromagnet willproduce feeble currents in,

3 is a cross section taken on the line 33 of electrodes 12 and 12 of amicrophonic transmitter and associate in any suitable manner the sounl-producing mechanism with the circuit which includes said electrodesand the carbon granules 14 which separate them.

In the particular embodiment of my 1nvention which is shown in thedrawings, the support 2 which maybe of brass, is secured to the base 1,which may be of any suitable material, and carries the bolts 3, 3, whichmay be threaded through said support 2 and held in position bylock nuts.The cross piece 5is secured to said bolts on one side of said supportand the cross piece 4 is secured to the bolts on the other side of saidsupport. The frame 16 to which the fixed electrode 12 andcarbon-containing capsule are secured is bolted to the frame 2 andaffords means for connecting said fixed electrode to the binding post'0. The movable electrode 12 is secured to the screw 13, and the screw13 and aluminium frame 17 are secured to the diaphragm 8 by means of thenut 13. The armature 7 of the cleetromagnet 6, 6 is threaded on theprojecting end of the screw 13. A lock nut 15 is employed to secure themica diaphragm 23 between the carbon containing capsule 15 and the nut22. As shown more clearly in Fig. 1, the carbon containing capsule 15 isknurled for purposes of ready adjustment and when adjusted is secured inthe frame 16 by a set screw 16.

The diaphragm 8 may be secured to the support 2 by means of the springs10 which carry rubber washers on their ends, and as shown the diaphragm8 may have its periphery covered by a rubber washer 9 or other suitablematerial for insulating it from said support 2.

The wire as is secured to the insulating block 24 and is connectedthrough the binding post (i to the battery B and the primary I of thetransformer M. The Wire y is connected to the frame 2, which as abovestated, is conductively connected to the fixed electrode 12 through theframe 16. As most clearly shown in Fig. 2, the wire .73 is conductivelyconnected to the movable electrode 12 through the intermediary of thelock nut 22 and the screw 13. The wire y is then connected through thebinding post 0 to the primary of the transformer M, thus completing thecircuit through the two electrodes 12, 12, the carbon granules 14,battery B and the primary of the transformer M.

In lieu of employing an electromagnet connected in series with the coils6, 6 for the purpose of retracting the diaphragm 8 and its attachedelectrode 12, I use a mechanical retracting means consisting of anelastic member so tensioned that the force exerted by it to move theelectrode 12 back to its normal position varies directly over a Widerange of positions of said electrode approximately as the force exertedthereon by the'electromagnets 6, 6. For this purpose a wire 20 se. curedto the extension 18 of the frame 17 by the nut 19 may be employed, andits tension may be adjusted by the adjusting screws 20 which arethreaded through the bolts 3, 3. When said wire is so constructed andarranged that its tension varies as the square of its deflection, itwill be evident that the movable electrode 12 and the moving partssecured thereto are in a condition of stable equilibrium, for the forceexerted on said movable electrode by the electromagnets 6, 6 variesinversely as the square of the separation of the armature 7 from thecores of said electromagnets. By thus maintaining, the movable electrodein a condition approximating closely that of stable equilibrium duringthe operation of the apparatus, it will be apparent that during suchoperation of said apparatus the only work required to be done by themagnetic flux developed in the electromagnets 6, 6 is the overcoming ofthe inertia of the movable electrode 12 and its connected moving partsas distinguished from the overcoming of the inertia of said parts and aretractile force. In this man ner, the variations effected in theresistance of the circuit of the battery B and microphonic transmitterare greatly amplified with the result that the sounds produced by a telephone receiver included in said circuit are much louder than they wouldbe were the usual magnetic retractile force employed in lieu of themember 20 and also distortion is greatly diminished. Instead ofconnecting the telephone receiver directly in thecircuit of the batteryB and microphonic transmitter, I prefer to connect said telephonereceiver T in series with the secondary I of the step-up transformer M,the primary of which is included in series with the battery B andmicrophonic transmitter, inasmuch as such arrangement results in a stillfurther amplification.

By inclosing the apparatus in the bell-jar and evacuating said jar, asby an air pump attached to the orifice 21, the movement of the electrode12 which is effected by the feeble magnetic forces which operate uponthe armature 7 may be increased on account of the resulting reduction offriction, and-the current variations created in the circuit of thebattery B may be correspondingly amplified. For the purpose ofmaintaining the vacuum in the bell-jar 25, the binding posts a b c (2,may extend through the base 1 and the external circuits of the magnets6, 6 and the micro honic transmitter may be connected to t e lower endsof said binding posts as indicated in the dotted lines in Fig. 1.

I claim 1. In an apparatus for amplifyingelectric currents varying inaccordance with sonorous vibrations, a microphonic transmitter com- IIOprising a fixed and a movable electrode, magnetically operated means formoving said movable electrode in one direction and mechanical means formoving said electrode in the opposite direction, said mechanical meansbeing so constructed that its tension varies as the square of itsdeflection.

2. In an apparatus for amplifying electric currents varying inaccordance with sonorous vibrations, a microphonic transmittercomprising a fixed and a movable electrode and means maintaining saidmovable electrode in a condition of stable equilibrium during theoperation of the apparatus.

3. In an apparatus or amplifying electric currents varying in accordancewith sonorous vibrations, an armature, a microphonic transmittercomprising a fixed and a movable electrode, means securing said movableelectrode to said armature, magnetic means for actuating said armature,and mechanical means secured to said movable electrode and exertingthereon a force in opposition to the force exerted thereon by saidmagnetic means, said mechanical means being so constructed that theforce exerted thereby on said movable electrode varies for all positionsof said electrode directly as the force exerted thereon by said magneticmeans.

4. In an apparatus for amplifying electric currents varying inaccordance with sonorous vibrations, a microphonic transmittercornprising a fixed and a movable electrode, an armature secured to saidmovable electrode, magnetic means for moving said movable electrode inone direction, and an elastic member secured to said movable electrodefor moving the same in the opposite direction, said elastic member beingso construct ed that the force exerted thereby on said movable electrodevaries for all positions of said electrode directly as the force exertedthereon by said magnetic means.

5. In an apparatus for amplifying electric currents varying inaccordance With sonorous vibrations, a microphonic transmittercomprising a fixed and a movable electrode, an armature secured to saidmovable electrode,

magnetic means for moving said electrode in one direction and a wiresecured to said mov able electrode for moving the same in the oppositedirection, said wire being so tensioned that the force exerted therebyon said movable electrode varies for all positions of said electrodedirectly as the force exerted thereon by said magnetic means.

In testimony whereof, I have hereunto subscribed my name this 17th dayof May 1906.

JOHN STONE STONE.

Witnesses GEO, Ix. W'oonwonrn, E. B. TOMLINSEN.

